1. Filed of the Invention
The present invention relates to an inkjet head of in inkjet recording apparatus, which ejects ink onto a recording medium to perform printing thereon.
2. Description of the Related Art
In inkjet heads, ink supplied from an ink tank is distributed from a common ink chamber to a plurality of pressure chambers, and a pulsed pressure wave is applied selectively to each pressure chamber so as to eject ink from a nozzle communicating with the pressure chamber. Of such inkjet heads, some have an ink reservoir for reserving ink supplied from the ink tank and supplying the reserved ink to the plurality of pressure chambers in order to supply ink to the pressure chambers stably.
In an ink channel from the ink tank to each nozzle through the ink reservoir, each pressure chamber, etc., there occurs a fluctuation of ink pressure due to a water hammer phenomenon etc. caused by ink inertia when the ink is supplied from the ink tank. In this event, in spite of a pulsed pressure wave applied to the pressure chamber at predetermined timing, there is a case that ink cannot be ejected normally from the nozzle due to the influence of the fluctuation of pressure in the channel. In such a case, the accuracy of ink ejection is lowered. Therefore, an inkjet head having a pressure fluctuation absorbing unit for suppressing the aforementioned fluctuation of pressure has been proposed.
For example, there is an inkjet head in which a flexible sealing film for sealing an opening portion of an ink reservoir is provided in an upper end portion of the ink reservoir communicating with a common ink chamber (for example, see JP-A-2003-145761 (Page 6, FIGS. 1 and 2)). In this inkjet head, the surface of the sealing film on the opposite side to the ink reservoir is exposed to the outside in the position of the opening portion of the ink reservoir. Accordingly, the sealing film can be deformed so that the fluctuation of ink pressure in the ink reservoir can be absorbed by the deformation of the sealing film.
There is also an inkjet head in which a diaphragm is provided to define a common ink chamber communicating with pressure chambers and a damper chamber and to attenuate oscillation of ink pressure in the common ink chamber in order to absorb pressure waves (backward components) propagating from the pressure chambers to a manifold when a pulsed pressure is applied to the pressure chambers (for example, see Japanese Patent Laid-Open No. 141856/1998 (FIG. 1)).